Effervescent tablet

ABSTRACT

A stable cleansing tablet, for example, for dentures, which dissolves in a favorable time to form a clear, non-foamy, oxygeneffervescent solution and which comprises certain proportions of sodium perborate monohydrate, alkali metal salt of dichloroisocyanurate, benzoic acid or salts thereof, phosphate salts, and chloride salts.

reece et al.

[111 3,821,117 June 28, 1974 [22] Filed:

[ EFFERVESCENT TABLET [75] Inventors: Jean Breece, North Brunswick;

Michael Brown, Hightstown, both of NJ.

[73] Assignee: Carter-Wallace, Inc., New York,

July 2 3, 1971 [21] Appl. No.: 165,394

[52] US. Cl 252/99, 8/109, 252/186, 252/187, 424/53, 424/130, 424/149 [51] Int. Cl Clld 7/56 [58] Field of Search 252/99, 186, 187; 8/109; 424/130, 53, 149

[56] I "References Cited UNITED STATES PATENTS 2,931,776

4/1960 Howard 252/99 3,706,670 12/1972 Gray ..252/99X FOREIGN PATENTS OR APPLICATIONS 1,049,051 11/1966 Great Britain 252/99 Primary ExaminerMayer Weinblatt Attorney, Agent, or FirmKevin B. Clarke 5 ABSTRACT 14 Claims, N0 Drawings- 1' EFFERVESCENT TABLET BACKGROUND OF THE INVENTION The present invention lies in the field of cleansing tablets. More specifically, the invention involves a tablet which can be placed in water wherein it dissolves to form a solution which is useful for cleansing articles such as artificial dentures by immersion therein. As used herein, the term cleansing jointly encompasses cleaning, bleaching, destroying or retarding growth of microorganisms, deodorizing, and the removal of particulate matter.

Also as used herein, the term denture includes artificial teeth, removable orthodontic bridges and denture plates. Such dentures'are usually constructed of porcelain or plastics such as phenolformaldehyde, acrylic and cellulose acetate resins, and metals such as alloys of chromium and cobalt.

A very important property sought in a denture cleanser is a high degree of overall cleaning including the removal of films, particles and debris. Another important property is the capacity to remove stains caused by substancessuch as coffee, tea or tobacco smoke without harming the porcelain, plastics or metals of the dentures. A further desirable property is the ability to destroy or retard the growth of microorgan- ISmS.

Numerous types of artificial denture cleansers have heretofore been suggested and marketed but none of them have been found to be entirely satisfactory.

For example, certain of the cleansers of the prior art are acidic, that is, they utilize a pH of about 7 or less in order to achieve sufficient cleansing. However, such acidity exerts a corrosive or otherwise adverse effect upon metals or other portions of the dentures.

On the other hand, another series of cleansers depend upon a relatively high degree of alkalinity to produce a cleansing action. Of course, a high degree of alkalinity, for example, a pH of about 12 or more can cause damage to denture structure and in addition results in a product which is not convenient to use.

'In any event, previously known denture cleansers generally fall into two main classes: the immersion type designed specifically for complete submersion of the denture in the cleansing solution; and, the paste or powder type cleanser which is mechanically applied. With immersion cleansers, the denture is soaked in a solution provided by dissolving a powder or tablet in warm water after which it is removed, rinsed and returned to the mouth. Such cleansers, if they are to provide a sufficient degree of cleansing, generally require an undesirable high or low pH AS noted above. In addition, the simple immersion cleansers are often deficient in removing stains and/or particulate matter, for example, food debris, which adheres to the surface and which is found in the crevices of the denture. In regard to the paste or powder type cleansers, adequate cleansing can be achieved by mechanical action, for example, brushing, but this is inconvenient and creates the risk of dulling the'otherwise smooth polished surfaces of the denture which in turn allows a more rapid redeposition of tartar and subsequent staining.

The art has provided partial solutions tothese denture cleansing problems. One step in the right direction has been the provision of effervescent formulations in the form of powders or tablets which dissolve and release an effervescent gas such as carbon dioxide or oxygen. The gas bubbles, as they pass the denture, contribute a gentle mechanical cleaning action and thus help to remove particulate matter. In addition, when oxygen contacts the denture, it tends to remove stains thereon and provide antiseptic action.

As just indicated, denture cleansing compositions can beprepared in the form of unitary tablets and this is highly desirable because of the convenient handling characteristics possessed by these tablets. Such tablets obviate the need for measuring and eliminate spillage problems normally encountered with granular compositions.

However, in formulating denture cleanser tablets which effervesce oxygen severe problems have heretofore been encountered.

In particular, it has been difficult to formulate such a tablet which has sufiicient dry strength to withstand normal packaging and handling and yet which dissolves rapidly when placed in water.

Moreover, in the case of oxygen releasing tablets, it

has been found desirable to utilize a relatively high pH to provide a medium in which oxygen is relatively insolubleso that the' oxygen bubbles will effervesce at a rapid rate to obtain a mechanical type cleansing action as'these bubbles pass the denture. However, too high a pH, for example, greater than about 12, should be avoided for safety reasons and to prevent excessive effervescence.

In addition, activators which have been used to trig-- ger release of oxygen from oxygen precursors such as perborates, persulfates or peroxides, as well as tablet lubricants or diluents, often resultin hazy or cloudy solutions or contribute an objectionable odor. A clear so lution is highly desirable from the standpoint of avoiding the redeposition of any materials which would contribute toward a dulling film, and a pleasant odor is, of

course, desirable for cleansing products.

Still other prior art formulations tend to foam during use which can cause spillage and obscure'visual examination of the cleansing progress.

SUMMARY OF THE INVENTION 5 In view of the need in the art as just described, the present invention provides a stable cleansing tablet which when added to water dissolves at a favorable rate to fonn a clear, non-foamy, oxygen-effervescent solution of pH 10.0 to 11.8. This tablet has strength and structural integrity, yet it readily dissolves in 2 to 40 minutes when placed in water. The tablet composition of the invention which achieves these desirable results comprises: 12-30 percent sodium perborate monohydrate; 59 percent alkali metal salt of dichloroisocyanurate; 420 percent benzoic acid or salts thereof; 30-75 percent phosphate salts; and 0-10 percent chloride salts.

Another novel contribution to this art can be found in the commonly assigned application of Herman E.

Jass and Frederick F. Kohlhepp entitled Effervescent Composition, Ser. No. 165,395, filed concurrently herewith.

DETAILED DESCRIPTION A detailed listing of the cleanser compositions of the present invention is set forth in Table I.'

TABLE I TABLET COMPOSITION Broad Composition Preferred Composition Most Preferred Comnosition It has been discovered as a part of this invention that the composition and proportions of ingredients of Table I provide an extremely effective and convenient effervescent denture cleanser. All of these ingredients cooperate in the control of oxygen generation and effervescence, pH, and/or cleansing. However, when :these ingredients are combined and pressed into tablet form in a conventional manner without the benzoic acid compound, the tablets thus formed take a prolonged time to dissolve.

Accordingly, it has further been discovered as a part of this invention that the addition of benzoic acid or salts thereof to the composition, prior to compression into a tablet, provides an unexpected and significant decrease. in the dissolution time.

Thus, tablets having the composition of Table 1 possess the following characteristics:

When these tablets are added to water, for example, to 50 parts by weight water at 35 C. to 45 C., they readily dissolve without agitation in 2 to 40, preferably 6 to 30 minutes to form a clear, non-foamy solution having a pH within the ranges indicated.

In aqueous solution within this pH range, the dichloroisocyanurate compound releases available hypochlorite which provides a known antiseptic effect. More importantly, the hypochlorite reacts with the sodium perborate monohydrate and activates its release of free oxygen into the system. Oxygen is, of course, a known antiseptic and bleaching agent.

Also within the pH ranges indicated, oxygen has. a low degree of solubility in aqueous solutions and thus the oxygen released to the solution by the sodium perborate monohydrate compound naturally effervesces. The composition of the tablets is so balanced that the effervescence commences immediately upon contact with water and continues at a desirable rate for a period of from 3 to 60 minutes, preferably 5 to 30 minutes. In addition, the composition of the tablets is such that the oxygen is released in the form of small bubbles. This is desirable since large bubbles could tend to lift the denture out of the cleansing solution.

Such effervescence of small oxygen bubbles insures intimate contact of oxygen with the surface and crevices of the denture to provide a high level of stain removal therefrom. Further, the small bubbles effervesce at a rate sufficient to provide a mechanical or scrubbing action as they pass the denture and thus physically assist in the removal of particulate matter.

It is to be noted that the proportion of sodium perborate monohydrate compound to dichloroisocyanurate compound is such that substantially complete consumption of hypohalite is realized prior to cessation of effervescence thereby avoiding undue release of free chlorine from the solution with its accompanying objectionable odor.

With further reference to Table l and the ingredients listed therein, the sodium perborate monohydrate has the empirical formula NaBQ H O and is commercially available as a dry granular material. Although other oxygen precursors including other perborates are available in the art, the specific selection of sodium perborate monohydrate in this invention is important to achieve the desired rate and type of oxygen effervescence as well as tablet dissolution.

Alkali metal, for example, sodium or potassium, dichloroisocyanurates are also commercially available in granular form. Of these, the sodium salt is preferred on the basis of solubility and stability.

The tablet composition contains 30 to percent phosphate salts. Illustrative of useful salts are tribasic phosphates, orthophosphates, tripolyphosphates, hexametaphosphates, pyrophosphates, polyphosphonates and the like. Suitable cations in these phosphate salts are sodium, potassium, ammonium, calcium, magnesium and the like.

As noted in Table I, preferred phosphate salts are sodium tripolyphosphate, trisodium phosphate and so dium hexametaphosphate, preferably utilized in certain proportions. This particular combination of phosphate salts has been found to provide the effervescent tablets of this invention with outstanding denture cleansing properties. Each of these ingredients is commercially available in granular and/or powder form.

- The tablet composition can also contain up to 10 peri cent chloride salts such assodium, potassium, lithium, calcium or magnesium chloride. Of these sodum chloride is preferred.

A characterizing component of the tablet composition is benzoic acid or a salt thereof collectively referred to herein as a benzoic acid compound." Preferably, the benzoic acid compound is selected from benzoic acid, ammonium, alkali metal, and alkaline earth metal salts of benzoic acid, and mixtures thereof. Most preferably, the benzoic acid compound is sodium benzoate. As just indicated, mixtures of the above enumerated compounds can also be used.

Sodium bcnzoate, the preferred benzoic acid compound of the tablet compositionfis also commercially available in granular or powder form. Sodium benzoate has the empirical formula NaC H O and has been heretofore utilized in minor amounts as a mold release agent in various types of tablets.

Other than the usual adjuvants such as minor amounts of dyes, perfume and the like, the tablet compositions of this invention are preferably limited to the ingredients of Table 1. However, if desired, other ingredients normally used in cleaning compositions can be included. Examples of such ingredients are surfactants such as soaps or synthetic detergents, sequestrants such as salts of ethylene diamine tetraacetic acid (EDTA) or nitrilotriacetic acid (NTA), and builders and/or fillers such as sodium silicate or sodium sulfate.

In use, the tablets are preferably placed in vl to 50 parts, most preferably 20 to 40 parts of water at 20 C. to 60 C., preferably 35 C. to 45 C. and allowed to dissolve, for example, in the presence of the denture, without stirring or other agitation being needed.

After a suitable period of time, for example, 3 minutes to 60 minutes, preferably 5 minutes to minutes, the dentures can be removed from the solution and readily rinsed. These dentures will be physically and bacteriologically clean. in addition, they will have a desirable clean taste and clean feel.

Conventional methods can be employed to produce the tablets of this invention. For example, the ingredients can be dry blended, segregated into tablet-size portions, and then compressed into tablets of the desired weight and shape.

As noted before, it is important that the benzoic acid compound be incorporated with the other ingredients prior to compression into tablets. Such a procedure provides uniform distribution of the benzoic acid compound within the tablet matrix. It has been found that this distribution is necessary for this component to exert its improvement effect upon the tablet dissolution time.

Suitable parameters for the tablets are as follows: A composition bulk density of 0.4 to 1.2 grams/cc, preferably 0.8 to 1.0 grams/cc, prior to compression and a tablet density of 0.5 to 1.5 grams/cc, preferably 0.8 to 1.3 grams/cc after compression. Each tablet can weigh from 0.1 grams to 10.0 or more grams, preferably from 3.0 to 7.0 grams and can be from 0.1 to 0.5 or more, preferably 0.2 to 0.35 inches thick. Conventional apparatus, for example, a Carver press, a single punch press, or a rotary press, can be used for the tabletting, and compression pressures can range from 2,000 pounds per square inch to 16,000 pounds per square inch, preferably from 6,000 pounds per square inch to 12,000 pounds per square inch.

ln preparing the tablets, it has been found preferable to first blend the ingredients of the composition together, then apply heat, for example, 35C. to 55 C. for 30 minutes to 24 hours, followed by compression and hermetic packaging, the entire operation being performed under conditions of low humidity, for exampic. 10 percent relative humidity at 70 F. Altematively. the heat can be applied subsequent to compression.

All percentages, parts and portions herein are by weight unless specifically stated otherwise. All references to 'pH are based on a 2.5 percent aqueous solution.

EXAMPLE 1 Tablets of 4.1 grams each and 0.25 inch thickness were prepare'dby dry blending the ingredients of Table 11, heating at 55 C. for 18 hours, and compressing in a single punch press at 12,000 pounds per square inch,

while at a relative humidity of less than 10 percent at 70 F.

These tablets were strong and did not crumble or break when subjected to normal handling, packaging and shipment. When any one of the tablets was placed in 150 grams of 40 C. water, the tablet dissolved within 26.6 minutes without agitation to form a clear, nonfoamy solution of pH 11.1. lmme'diately upon placement of the tablet in the water, small bubbles of oxygen effervesced at a rapid rate and this effervescence continued for 30 minutes.

In order to evaluate the denture cleansing properties of the tablets of Example 1, an artificial soil'consisting of lamp black dispersed in a mixture of hydrogenated vegetable oil and a liquid fatty acid and known to cause staining of dentures was prepared and smeared in the marginal and cervical areas of test sections of a denture. These test pieces were then conditioned for 19 hours at 40 C. One tablet was then placed into a beaker containing 150 cc of water maintained at 40-45 C. with subsequent effervescence. A treated denture section was placed in the beaker and allowed to remain for 15 minutes and then removed. After rinsing, the test pieces were visually checked for degree of soil removal. The test pieces rinsed free of all soil and were clean. 1n

comparison, pieces treated in the same manner as just described using one of the leading commercially available cleanser tablets required additional brushing to remove all traces of soil.

Sections of a denture, teeth and gum surfaces, were exposed, to cigarette smoke from a given number of cigarettes in a closed vessel over a period of several minutes allowing for a substantial film of tar and nicotine to be deposited on the exposed surfaces. The stained sections were cleansed as above. Having soaked in the cleansing solution for 30 minutes at which time a preliminary check indicated them to-be clean, they were then removed and rinsed. In all instances, the pieces which had been immersed in the solution were totally cleansed. Similar sections immersed in a solution from one of the leading commercially available cleanser tablets were less efficiently cleansed even after 8 hour exposure.

Commercially available denture adhesive powders and pastes were applied to test pieces of a denture and placed in cleansing solutions prepared from tablets as above. After 30 minutes the adhesives had been sufficiently' loosened to allow easy removing with rinsing andslight mechanical agitation.

The antiseptic properties of the cleanser tablets of this Example were evaluated in the following manner. Saliva samples were obtained from two denture wearers by having each rinse his mouth with sterile aliquots of saline solution. These aliquots in turn were added to sterile alternative thioglycollate medium and incubated at 37 C. for 48 hours. Thoroughly mixed, the resultant culture was used as the inoculum for the following tests. One tablet was dissolved in 140 gram portions of room temperature water and the solutions were inoculated after 2 /2, 5, 10, 20, 40, 80 and 160 minutes with ml of inoculum. The microorganisms in the inoculum were completely killed when exposed for a 10 to minute contact period.

Additional experimental work was conducted with the tablets of Example I to illustrate the affect of the sodium benzoate component on the dissolution time.

Table III shows the same tablet composition of Table 11 except that the amount of sodium benzoate was var- .ied. It can be seen from these data that a highly significant improvement in dissolution time is achieved with about 4 percent sodium benzoate but that amounts greater than about 18-20 percent are not further advantageous. The dissolution time was measured by dropping a tablet into a 250 cc beaker containing 150 'cc of 40 C. i 0.1 C. tap water in a constant temperature bath. Timing is started immediately. When the solution is clear and free from any visible signs of sedimentation at the bottom of the beaker, timing is stopped.

TABLE III TABLE [V DISSOLUTION TIME OF TABLETS PREPARED WITHOUT SODIUM BENZOATE IN SOLUTION OF SODIUM BENZOATE Dissolution Time of Tablets Prepared without Sodium Benzoate in their Matrix. 40C. Water Gram of Sodium Benzoate Predissolved in 150 Grams of Water DISSOLUTION OF TABLETS WITH VARYING QUANTITIES OF SODIUM BENZOATE Gram Avg. Dissolution Time (Total Weight Sodium Benzoate, Sodium Benzoate (min.) in Water at 40C. of Tablet, by Weight of Per Tablet with no stirring Grams) Tablet In Table IV, tablets of the same composition of Table II were prepared except that no sodium benzoate was added to the compressed tablet. Instead, from 0 to 1.0 grams of sodium benzoate was dissolved in various beakers each containing 150 grams of water at 40 C. and the tablets containing no sodium benzoate were allowed to dissolve in these various solutions of sodium benzoate. It would normally be expected that the dissolution times of the tablets would be further accelerated with sodium benzoate pr'edissolved in the water. However, quite unexpectedly, the dissolution time was not Th e data in Table V show the influence of sodium benzoate on the dissolution time of the individual ingredients of thetablet composition of Table II. In Table- V, the individual ingredients were allowed to dissolve alone as well as together with sodium benzoate at 40 C. in water with no stirring and the dissolution rates were compared. The sodium benzoate was not found to markedly influence the dissolving time of any individual ingredient, except perhaps the sodium perborate rrionohydrate, where the dissolution was somewhat retarded.

EFFECT OF SODIUM BENZOATE ON THE DISSOLUTION TIME OF INDIVIDUAL INGREDIENTS OF TABLE II COMPOSITION Dissolution Time Together with 0.3 Gram Sodium Ben- Dissolution Time of Ingredient Alone at 40C., Water,

zoate at 40C., Water, no no Stirring Ingredient Stirring Sodium Perborate Monohydrate 405 minutes 330 minutes Sodium Dichloroisocyanurate 23 minutes 17.5 minutes Sodium Tripolyphosphate 250 minutes 255 minutes Trisodium Phosphate 135 minutes minutes Sodium Chloride 15 seconds 1.5 seconds Sodium Hexametaphosphate 30 seconds 30 seconds shown to lengthen the dissolving time:

sodium perborate (163 minutes), sodiumbenzoate (153 minutes), sodium tripolyphosphate( 108 minutes), sodium dichloroisocyanurate (91 minutes).

TABLE VI DISSOLUTION TIMES OF TABLETS WITH ONE INGREDIENT AT A TIME ELIMINATED FROM THE TABLE II COMPOSITION IN 40C. WATER, WITHOUT STIRRING Average Ingredient Eliminated Dissolution Time (minutes) g Sodium Perhorate Monohydrate 1 163.3 Sodium Dichloroisocyanurate 91.6 Sodium Tripolyphosphate 27.3 Trisodium Phosphate 108.0 Sodium Chloride 24.0 Sodium Hexametaphosphate 26.0 Sodium Benzoate 153.3

The data in Table VII indicate the dissolving time for tablets consisting of only sodium perborate monohydrate and sodium dichloroisocyanurate compressed as tablets with varying quantities of sodium benzoate. While the sodium benzoate can be seen to decrease the dissolving time required in a similar manner to the sodium benzoates effect on the full composition (Table II). it should be noted that tablets of only these three ingredients require a longer time to dissolve than the complete Table II tablet composition with a corresponding quantity of sodium benzoate. In addition, tablets of only these three ingredients were found to be inferior to the Table II composition in cleaning ability,

especially of dentures stained with tobacco smoke and tars.

10 TABLE VII THE EFFECT OF VARIOUS QUANTITIES OF SODIUM BENZOATE ON THE DISSOLUTION TIME OF TABLETS CONTAINING ONLY SODIUM PERBORATE MONOHYDRATE (1.10 GRAMS) AND SODIUM DICHLORO' ISOCYANURATE (0.3 GRAMS) IN 40C., WATER, WITHOUT STIRRING l0 Average Gram of Sodium Dissolution (Total Tablet Benzoate Per Tablet Time (minutes) Weight, Grams) In the following Examples, tablets as shown in Table VIII are prepared in accordance with Example I and will perform in a' substantially equivalent manner.

TABLE viii Although described herein in terms of their primary utility as denture cleansers, it is apparent that the tablets of this invention can-be otherwise used. For example, the tablets are useful for cleansing dishes, sinks, toilet bowls and the'like.

Asused herein, the term non-foamy" refers to a substantial absence of foam but does not mean an absolute absence of foam since the desired effervescence does, of course, result in a minor accumulation of bubbles on the liquid surface.

What is claimed is: g

1. A stable denture cleansing tablet which when added to water dissolves in 2 to 40 minutes to form a clear, non-foamy, oxygen-effervescent solution of pH 10.0 to 'l 1.8 said tablet consisting essentially of:

10-30% Sodium perborate monohydrate 5-9% Alkali metal salt of dichloroisocyanurate 420% of a benzoic acid compound selected from the group consisting of benzoic acid, ammonium and Percent By Weight Ingredient Ex. III Ex. IV

2s 2s 24 26 so ll 11 alkali metal, salts of benzoic acid, 511a miirtures thereof,

30-75% Phosphate salts selected from the group consisting of the sodium, potassium and ammonium tribasic phosphates, orthophosphates, tripolyphosphate hexametaphosphates, pyrophosphates or polyphosphonates,

-10% Chloride salts selected from the group consisting of the sodium potassium lithium, calcium or magnesium chlorides.

2. The tablet of claim 1 which when added to water effervesces oxygen immediately.

3. The tablet of claim 2 where the effervescence continues for a period of from 3 to 60 minutes.

4. The tablet of claim 1 consisting essentially of:

22-28% Sodium perborate monohydrate 6-9% Sodium dichloroisocyanurate 4-10% of a benzoic acid compound selected from the group consisting of benzoic acid, ammonium and alkali metal salts of benzoic acid, and mixtures there,

45-65% Phosphate salts selected from the group consisting of the sodium potassium, ammonium, calciuin and magnesium tribasic phosphates, orthophosphates, tripolyphosphates, hexametaphosphates, pyrophosphates or polyphosphonates.

5. The tablet of claim 4 wherein the benzoic acid compound is sodium benzoate.

6. The tablet of claim 5 which contains 2-8percent sodium chloride.

7. The Tablet of claim 6 wherein the phosphate salts consist, based on the total tablet of: I

-25% sodium tripolyphosphate -35% trisodium phosphate 0.5-5% sodium hexametaphosphate.

8. The tablet of claim 7 which dissolves to form a solution of pH of 10.8 11.3.

9. The Tablet of claim 8, consisting essentially of 26-28% sodium perborate monohydrate 6-8% sodium dichloroisocyanurate 6-8% sodium benzoate 21-23% sodium tripolyphosphate 28-30% trisodium phosphate 2-5% sodium hexametaphosphate 3-5% sodium chloride.

10. The tablet of claim 9 which when added to 10 to 50 parts by weight water at 35 to 45 Centigrade dissolves in 6 to minutes without agitation.

11. The tablet of claim 10 which has a pH of about 11.1.

12. A method for decreasing the dissolution time of an effervescent denture cleansing tablet consisting essentially of 10 to 30 percent sodium perborate monohydrate, 5 to 9 percent of an alkali metal salt of dichloroisocyanurate and 30-75% phosphate salts selected from the group consisting of the sodium, potassium, ammonium, calcium and magnesium tribasic phosphates, orthophosphates, tripolyphosphates, hexametaphosphates, pyrophosphates and polyphosphonates and O to 10 percent chloride salts selected from the group consisting of the sodium, potassium magnesium,

zoic acid and mixtures thereof.

13. The method of claim 12 wherein the compound added is 6 to 8 percent sodium benzoate.

14. The method of claim 13 wherein after addition of the sodium benzoate and prior to-compression, the ingredients are heated. 

2. The tablet of claim 1 which when added to water effervesces oxygen immediately.
 3. The tablet of claim 2 where the effervescence continues for a period of from 3 to 60 minutes.
 4. The tablet of claim 1 consisting essentially of: 22-28% Sodium perborate monohydrate 6-9% Sodium dichloroisocyanurate 4-10% of a benzoic acid compound selected from the group consisting of benzoic acid, ammonium and alkali metal salts of benzoic acid, and mixtures there, 45-65% Phosphate salts selected from the group consisting of the sodium potassium, ammonium, calcium and magnesium tribasic phosphates, orthophosphates, tripolyphosphates, hexametaphosphates, pyrophosphates or polyphosphonates.
 5. The tablet of claim 4 wherein the benzoic acid compound is sodium benzoate.
 6. The tablet of claim 5 which contains 2-8percent sodium chloride.
 7. The Tablet of claim 6 wherein the phosphate salts consist, based on the total tablet of: 20-25% sodium tripolyphosphate 25-35% trisodium phosphate 0.5-5% sodium hexametaphosphate.
 8. The tablet of claim 7 which dissolves to form a solution of pH of 10.8 - 11.3.
 9. The Tablet of claim 8, consisting essentially of 26-28% sodium perborate monohydrate 6-8% sodium dichloroisocyanurate 6-8% sodium benzoate 21-23% sodium tripolyphosphate 28-30% trisodium phosphate 2-5% sodium hexametaphosphate 3-5% sodium chloride.
 10. The tablet of claim 9 which when added to 10 to 50 parts by weight water at 35* to 45* Centigrade dissolves in 6 to 30 minutes without agitation.
 11. The tablet of claim 10 which has a pH of about 11.1.
 12. A method for decreasing the dissolution time of an effervescent denture cleansing tablet consisting essentially of 10 to 30 percent sodium perborate monohydrate, 5 to 9 percent of an alkali metal salt of dichloroisocyanurate and 30-75% phosphate salts selected from the group consisting of the sodium, potassium, ammonium, calcium and magnesium tribasic phosphates, orthophosphates, tripolyphosphates, hexametaphosphates, pyrophosphates and polyphosphonates and 0 to 10 percent chloride salts selected from the group consisting of the sodium, potassium magnesium, lithium and calcium chlorides which method consists of adding to said ingredients in dry form, prior to compression into a tablet, from 4-20 percent of a benzoic acid compound selected from the group consisting of benzoic acid, ammonium and alkali metal salts of benzoic acid and mixtures thereof.
 13. The method of claim 12 wherein the compound added is 6 to 8 percent sodium benzoate.
 14. The method of claim 13 wherein after addition of the sodium benzoate and prior to compression, the ingredients are heated. 